Process and apparatus for treating solid fuel materials

ABSTRACT

Solid fuels, such as contaminated biomass and solid city waste, are converted into a synthesized gas by gasification and exploitation of the energy contained in the fuels. The fuel is gasified an a co-current gasogen ( 1 ), while the cinders are separated, removed and purified after a fraction of the fuels has undergone combustion and before the fuel has been gasified. Cinder purification is made by complete combustion, while the fuel that has undergone the gasification step without being completely transformed in CO is recirculated by mixing it to fresh fuel material. The process is carried out in an apparatus comprising a vertical co-current gasogen ( 1 ) and a device for the separation and removal of cinders ( 16,19,5,6 ) as well as a scorification chamber ( 3 ) where cinders are purified from accompanying fuel material by complete combustion and are then collected in a waste tank ( 28 ).

This invention is concerned with a process for treating solid fuels,such as contaminated biomass and solid city waste, and for convertingthem into a synthesized gas by gasification carried out in a co-currentgasogen. The invention is also concerned with an apparatus for carryingout the process.

Several processes are known in the practice and the patent literaturefor treating solid fuel materials, and particularly contaminated biomassand solid city waste, by transformation of the fuel materials into asynthesized gas, from which energy is then retrieved in different ways,e.g. directly in form of heat energy, or indirectly by generation ofelectric power.

According to a process disclosed in detail, for instance, in EP-0 663433, the fuel is first compacted in a tubular channel of preferablycircular cross-section, then thermally treated by a process ofgasification and pyrolysis, with generation of a synthesized gas in thetubular channel, and the carbonized material after the above heattreatment, is finally submitted to complete combustion at the end of thechannel in a counter-current gasogen. In this known approach, cindersare separated only after complete combustion in the counter-currentgasogen, due to the circumstance that the cinders are collected on thebottom of the gasogen, and then fall down onto a water bed acting as asealing buffer to prevent gas exchanges between the gasogen and theoutside environment.

The above known approach has two main disadvantages. On the one hand, itis very difficult to have a sufficiently large gasification chamber,such that the necessary gasification step can be completed, this stepconsisting in the transformation of CO₂, as developed in the partialcombustion of a fraction of the material, into the CO synthesized gas,as is the object of the invention. As a matter of fact, the annulargasification chamber should, if its aim is to be attained, take anexcessive length, with considerable, and possibly unsurmountable,constructive problems. On the other hand, cinders are separated andremoved only after the complete combustion of the material in thecounter-current gasogen has taken place, so that the cinders contaminateevery step in the gasification process. It is apparent that it would beadvantageous to separate the cinders from the fuel as soon as possible,so that the operating steps can be more easily governed or controlled.

According to another known solution for a co-current gasogen, aspublished in EP-0 565 935, a vertical co-current gasogen comprises acombustion area for a fraction of the material, having an annular shape,where the oxidant is fed from both the inner and/or outer sides, and agasification chamber for the remaining material, which again is verticaland arranged above and downstream of the combustion area, in thedirection of displacement of the material.

This approach does in fact afford optimal conditions of gasification,inasmuch as it allows gasification chambers of practically unlimitedextension to be built, so as to insure complete transformation of theCO₂ generated into CO. Moreover, this solution also provides forrecirculating the material that has undergone the gasification stepwithout being completely converted into the synthesized gas. Suchrecirculation consists in allowing the above material to overflowlaterally at the end of the gasification chamber and to drop laterallywithin the gasogen to mix with the fresh material at the bottom.However, this solution is not suitable for use in the gasification ofsolid fuel materials producing cinders during combustion, such ascontaminated biomass and solid city waste, because it lacks a device forseparating, removing and purifying the cinders, which will thereforeremain in the gasogen and eventually clog it.

The object of the present invention is therefore to provide a processand an apparatus for treating fuel materials to convert them into asynthesized gas by gasification in a co-current gasogen, which can avoidthe above drawbacks of the prior art and which can insure conditions oftreatment of solid fuel materials, particularly contaminated biomass andsolid city waste, giving rise to optimal cinders. In other words, theprocess should meet all rules in force concerning protection of air andwater, and should be perfectly gorvernable and controllable, so that theapparatus can operate without interruption for long periods of time.

The above object is attained with a process for treating solid fuelmaterials, comprising a gasification step of the material in aco-current gasogen, according to the preamble of claim 1, having thefeatures recited in the characterizing part of claim 1.

The invention also concerns an apparatus for carrying out the processaccording to the preamble of claim 10 and having the features recitedthe characterizing part of claim 10.

Dependent claims 2 to 9 concern preferred embodiments of the inventiveprocess, and dependent claims 10 to 14 concern preferred embodiments ofthe apparatus for carrying out the inventive process, its advantagesappearing more distinctly in the following disclosure of a preferredembodiment of the invention.

The invention will now be further described with reference to an exampleof the apparatus concerned, shown diagrammatically on FIG. 1.

GENERAL DESCRIPTION OF THE INVENTION

The invention comprises two main units:

a vertical co-current gasogen 1, similar, in its main components, to theo gasogen disclosed in EP-0 565 935, to which is here made specificreference.

a system 2 for separating and removing “cinders” arising within thegasogen, and an associated, though geometrically distinct, device 3 forpurifying the cinders.

The term “cinders” is used to refer to all matter which is contained inthe fuel supplied to the gasogen and which is incombustible andconsequently not gasifiable. The mass percentage of cinders in the fuelcan vary in a wide range: generally in the range 0 to 50%.

The cinders may originate directly from the removal carried out withingasogen 1, or they may be part of the dusts retained in the severalpurification modules for the synthesized gas (cyclone filters, clothfilters, electrostatic filters). The material with a high cinder contentis conveyed, through a suitable duct, to purifying device 3, also calledscorification chamber. In this chamber, the material is suitably treatedso that only inert matter is obtained a final product

A connection duct 5 leading from gasogen 1 to scarification chamber 3 isprovided with a suitable material-conveying system 6, which, dependingon the geometrical relationship between the two main units, may consistin a horizontal auger 6 as shown, or in an inclined auger, or in asimple inclined chute, possibly of the vibrating type.

The inventive gasogen is of the kind having a recirculating bed, theflows of gas and of solid matter being co-current and orientedvertically. The heat required by the process is supplied by thecombustion of a predetermined fraction of the fuel supplied. The oxidantrequired for partial combustion may be, depending on circumstances,plain air, air enriched with oxygen, Or pure oxygen. In any case,particularly where air is used, the oxidant is pre-heated to atemperature above 400° C., by using a fraction of the available heatcontained in the synthesized gas coming out from gasogen 1 at a hightemperature (650 to 700° C.). Pre-heating allows the PCI of the gas tobe increased, while improving combustion at the same time.

If necessary, in order to increase the synthesis of gas molecules withhigh hydrogen content (H₂ hydrocarbons), a mixture of oxidant andoverheated steam may also be used.

The gasogen can operate either at atmospheric pressure or at higherpressures, in the range of a few tens of bars, so that the synthesis ofhydrocarbons is promoted (particularly CH₄).

The fresh fuel material fed by auger 7 is mixed to the carbon resultingas a residue of gasification and emerging from duct 8, and is thenpropelled into the gasogen by injector auger 9. Within gasogen 1, avertical auger 10 distributes the mixture uniformly over an extended,though narrow, annular surface, while, at the same time, lifting themixture to the combustion area 11.

Until this time, the flows considered have only been submitted tophysical operations. Chemical reactions start when the material reachesthe immediate neighborhood of the annular combustion area 11. Theoxidant atmosphere required for combustion is generated by blowingoxidant from the outside and from the inside of annular area 11.Combustion chamber 11 may be entirely built in a metal resistant to hightemperatures, or it may have parts of ceramic or refractory materialwhich will insure a long lifetime, particularly where pure oxygen isused as an oxidant in the process. Ceramic parts, or parts of a similarmaterial, allow the process temperature to be increased, because theyreduce the heat loss by conduction through metal walls. This helps thegasification process.

Under the action of high temperature, which is also favored by thephysical concentration of the combustion, and of the oxidant atmosphereprevailing in that area, the material undergoes a number of chemicalreactions, leading to the formation of gas and carbon (mainly pyrolyticand combustion reactions). The gas and carbon so generated move towardsthe top of gasification chamber 12, crossing carbon bed 13 locatedthere. During their passage, the pyrolysis/combustion gas and the carbonreact together chemically and physically until a final product isobtained which comprises the synthesized gas proper and the residualcarbon that has not reacted. The synthesized gas emerges from carbon bed13 and collects within rest chamber 14 (with the purpose of smoothinggas removal and of decanting a part of the suspended particulate) whichin turn leads to gas outlet duct 15. The residual carbon is collected bygravity in duct 8 to undergo a fresh gasification cycle. A portion ofthe cinders contained in the fuel is removed through duct 5 and isprocessed separately in scorification chamber 3.

The central shaft in the gasification chamber, which is integral withthe rotating vertical auger, is provided, at its bottom and top ends,with respective shovels 16 and 17, having the function of materialdistributors.

Lower shovels 16 are arranged turbine-like, i.e. with surfaces formingan angle to the vertical direction. As the shaft rotates, shovels 16 and17 push the surrounding material upwards, and leave a small empty cavityon their lower sides along the entire shovel lengths. The empty cavityis invaded by the gas formed in the underlying combustion and pyrolysis,which, in the absence of any substantial resistance, will be distributedradially over the entire surface. Shovels 16 and 17 have thus the taskof distributing the combustion-pyrolysis gas over the entire surface ofchamber 12 and, since there is a relative motion between the shovels andthe material, they also prevent the formation of preferential channelsin the passage of the gas. As it will appear below, shovels 16 also havethe function of helping separation between carbon and inert cinders, sothat the amount of fuel material to be treated in scorification chamber3 is reduced Upper shovels 17 are arranged horizontally and have merelythe task of conveying the excess carbon toward recirculation port 18.

Definition of Flows within the Gasogen

During operation of the apparatus, a hierarchy of the rated flow ratesof the several augers should at all times be maintained:

rated flowrate in vert, auger 10>rated flowrate in injector auger9>flowrate=in supply auger 7

The flow rates through vertical auger 10 and injector auger 9 are merelynominal as vertical auger 10, for instance, will convey at any giventime only what it receives from injector auger 9. In this case the flowrate through vertical auger 10 would be equal to the flow rate throughinjector auger 9. Similarly, injector auger 9 will convey at any giventime the flow rate of supply auger 7 plus the flow rate of therecirculated carbon. The balance of the flow rates is achieved due tothe variations of their efficiencies.

This hierarchy is imposed in order to prevent clogging between theseveral augers, which would have serious consequences for the mechanicsand the operation of the apparatus.

An important peculiarity of the inventive gasogen is the recirculationof the carbon that has not reacted during gasification. Therecirculation of a fraction of the carbon is already known from EP-0 565935 mentioned above, but the recirculation there is distinguished fromthe present invention because of the substantial difference between thebeds in the respective configurations.

The advantages of recirculation are several:

The recirculating carbon (having a substantially homogeneouschemio-physical composition) mixes with the fresh fuel before enteringthe gasogen, thus improving the homogeneity of the physical and chemicalcharacteristics of the material reaching the combustion area, andconsequently stabilizing that area.

The recirculating carbon reaching the combustion area, which is dry, hotand of a low grading, tends to burn before the fresh fuel with which itis mixed. This leads to a saving of a part of the pyrolized gasdeveloping from the fuel, which would otherwise be burned in thisoxygen-rich area.

The carbon acts as a filter and catalist with respect to severalsubstances, among which are tars. Since the bed recirculates, eachpassage through the combustion area regenerates the specific propertiesof the carbon, which would. otherwise be progressively lost.

The gasification chamber holds a bed comprising mainly carbon and inertmatter. Since the separation and removal device is unable to remove thetotality of inert matter, the recirculation prevents it fromaccumulating within the bed and progressively reduce the amount ofcarbon that can react and consequently also the efficiency of thegasification reactions. Due to recirculation, inert matter is brought tothe neighborhood of the cinder removal port 19, and its rate within thecarbon bed is maintained constant.

The amount of recirculating carbon is regulated by adjusting the ratiobetween the flow rates through supply auger 7 and through injector auger9. The larger the flow rate through injector auger 9 with respect to theflow rate through supply auger 7, the more carbon will be recirculated.Consequently, the material reaching the combustion area will have ahigher rate of carbon and a lower rate of fresh fuel.

The power developed in the gasogen is regulated by adjusting the flowrate of injected fuel. An increase in the oxidant flow rate will giverise to an increase in the output power generated by the gasogen, andvice-versa for a reduction. It is obvious that to a power variation ofthe gasogen will correspond a variation of the flow rate of the fuel inthe same direction; this will give rise, consequently, to a variation offlow rate in supply auger 7.

It should be noted that supply auger 7 is preferably not controlled byan operator directly, but rather it is governed by the level detectorplaced at the top of the carbon bed (not shown). This will provide tokeep the carbon level at a height that is always slightly above theheight of the recirculation port.

Scorification Chamber 3

The first step in the process of removal of inert matter or cinderscontained in the fuel takes place within gasogen 1, and moreparticularly on the bottom of gasification chamber 12. Due to therelative motion between lower shovels 16 and the material, a sort ofscrambling of the material is obtained. By taking advantage from thedifference in density and size grading of carbon and cinders, the lattercan be made to settle (or “decant”) on the bottom of chamber 12. Therotary motion of shovels 16 then pushes the cinders toward the removalport 16, where they are then removed.

Gasogen 1 and gasification chamber 12 are two physically quite distinctdevices. Communication between them takes place in form of materialremoved from gasogen 1 and conveyed to scorification chamber 3 and inthe form of combustion gas generated in scarification chamber 3 andreintroduced to gasification chamber 12 of gasogen 1.

As already mentioned above, the transport of the material can take placethrough a horizontal or inclined auger 6, by chute along an inclinedduct, or through any other transport device which is able to operate ata high temperature and which is able, at the same time, to insure acomplete seal.

During the transfer from gasogen 1 to scorification chamber 3,connections are also preferably provided with other transport systems20, which, for instance, convey dusts coming from the gas filteringdevice. It is thus possible to reduce solid emissions from gasogen 1 tothe mere inert matter coming from scorification chamber 3.

Operation of the Scorification Chamber

The material reaching the scorification chamber 3 comprises asubstantial fraction of inert material and a less substantial fractionof carbon, which is inevitably conveyed with the cinders.

The task of scarification chamber 3 is to purify the above heterogeneousmixture, so that its outlet delivers cinders only. This step raises theoverall efficiency of the apparatus and avoids the loss of the chemicalenergy inherent to the carbon, which would otherwise be wasted Moreover,the amount of cinders produced in the gasogen is reduced to a minimum.

Cinder purification is achieved by blowing a metered amount of oxygeninto scorification chamber 3 (in form of plain air, enriched air or pureoxygen), so that the carbon therein is completely burned. Oxygen may bederived off the primary air circuit of the gasogen, or it may besupplied by a fully independent air circuit. Gas produced by thecombustion of the material comprising almost exclusively CO₂, a COfraction and possibly N₂ (when using air as an oxidant), is, e.g.,subsequently added, through pipe 21, to the oxidant used in thecombustion of a fraction of the material so that it is partiallyreconverted to CO by exploiting the “purifying” properties of the carbonbed at the same time. In order to avoid disturbing the composition ofthe synthesized gas produced in gasogen 1, due, for instance, to theintroduction of excessive and unnecessary amounts of oxygen andnitrogen, and in order to avoid removal of carbon-containing materialfrom scorification chamber 3, the oxidant blown into the scorificationchamber should be as far as possible in the required stoichiometricratio.

The material comprising carbon and inert residue, emerging from gasogen1 through pipe 8 and/or coming from the gas filtering device 4 throughpipe 22, reaches scorification chamber 3 through auger 6. This materialis then engaged by auger 23 (which has a rated capacity larger thanauger 6) and conveyed to annular combustion area 24, where, due to airblowing to the outside periphery and to the high temperature, carboncombustion takes place. The combustion can proceed, if necessary, as faras distribution chamber 25. Combustion area 24 and distribution chamber25 are preferably built in a metal resistant to high temperatures or ina ceramic or refractory material.

The combustion gas is extracted through pipe 21 for reintroduction intogasification chamber 12. The spent cinders, on the other hand, areengaged by shovels 26, which are integral with the upper end of auger23, and are swept off through a chute 27 into a storage tank 28. Itshould be noted that the oxidant necessary for combustion in thescorification chamber 3 may be heated in heat exchanger 29, thusexploiting the heat contained in the hot cinders. This will cool thecinders, thus reducing the heating problems in the storage tank placeddownstream and increasing the overall efficiency of the apparatus. Anysensors required for process control are placed at the inlet of chute 21(not shown).

It should be noted that the material flow removed from the gasogendetermines the percentage of cinders in the carbon bed: the larger theflow, the less cinders will be present in gasification chamber 12. Onthe other hand, the higher is the flow of removed material the morecarbon is contained in it.

The simplest way to manage the operation of scarification chamber 3 isto set a fixed value for the material flow through auger 6 and anassociated value for the oxidant flow, so that the stoichiometric ratiois approached. These values can be established by means of tests made onthe apparatus during operation and then refined with operating practice.

A more accurate way of managing scarification chamber 3, which, however,requires suitable sensors, is to regulate the flow of oxidant blown in.If the stoichiometry of the combustion is to be satisfied, the oxidantflow rate corresponds to a given carbon flow rate. The material flowrate, which also contains cinders, is therefore determined as a functionof the prescribed oxidant flow rate and of the carbon content in thematerial.

The stoichiometry of combustion can be evaluated mainly in two ways:analysis of the O₂ content in the combustion gas and/or analysis of thetemperature of the combustion fumes. Through analysis of the presence ofoxygen in the fumes, any shortage or excess of fuel can be determined,and consequently an insufficient or excessive flow rate through auger 6.

Management by analysis of the fume temperature requires preliminarytests made on the operating apparatus, in order to determine thetemperature as a function of excesses or shortages in the flow rate ofthe waste material. After this determination has been made, a comparisonof the real fume temperature with the table of experimental values willshow which adjustments should be made to the auger flow rate.

In summary, the most important features in the present invention are asfollows:

a) Concerning the gasogen proper.

A fraction of the carbon bed is recirculated.

The recirculating carbon is mixed to the fresh fuel before reachingcombustion area 11.

Recirculation makes place outside the main gasogen structure.

The recirculation rate, as well as the material flow rate throughcombustion area 11 is managed by adjusting the flow rate of injectorauger 9: vertical auger 10 has just to convey all the material received.

The power of the apparatus is adjusted by changing the primary oxidantflow rate. Fuel consumption is adjusted by controlling the flow rate inthe supply auger.

Turbine-like shovels 16, integral with central shaft 30, homogeneouslydistribute the combustion gas over the entire surface of the bed, andavoid formation of preferential flow channels through the bed Shovels 16also help inert matter contained in the fuel to settle on the bottom ofthe gasification chamber and push the inert matter toward the removaloutlet 19.

Ceramic or similar parts are preferably installed in hot areas, in orderto increase the process temperature, improve gasification and prolongthe lifetime of such areas.

b) Concerning scarification chamber 3:

The scorification chamber 3 is physically distinct from gasogen 1, andcommunicates with it through cinders removal auger 6 and pipe 21, whichblows the combustion gas in.

It can handle flows having a high cinders content, originating fromgasogen 1 and from the gas-filtering device 4, by means of a number ofconnections such as 8, 22 leading into cinders removal duct 6.

It gives rise to a sold waste comprise only inert matter, with maximumreduction of its quantity and an improved overall efficiency of theapparatus.

It does not generate emissions, because the combustion fumes are addedto the oxidant and are reintroduced into combustion chamber 11, wherethey have a further chance to participate in the specific chemicalreactions a draw a benefit from the purifying properties of the carbonbed.

Combustion chambers 11 or 24 may be built in ceramic or in a similarmaterial.

The inventive process and apparatus can be applied in the heatingtreatment of any organic matter, in the widest meaning of the word(including matter of natural origin as well as matter of chemicalorigin, such as the several hydrocarbons, plastics, rubber, etc.), evenif they contain substantial amounts of inert, and thereforeincombustible, matter (as high as 50%). The peculiar mechanicalstructure has the ability to treat fuels of different sizes and shapes.More particularly, the process and apparatus of the invention can usecrumbled powders, briquettes, pellets, having a size or grading onlylimited by the mechanical conveying ability.

The resulting product is a so-called “weak” gas, having a chemicalcomposition and a flow rate depending on the fuel used, and capable ofbeing used to different purposes, such as direct combustion for beatingair, water or other desired fluid, or in the production of overheatedsteam for operating a turbine, or for operating a gas turbine or aninternal combustion engine. It could also be used as a starting materialin the chemical industry (synthesis of ammonia, methanol etc.).

What is claimed is:
 1. A process for treating solid fuel materials, suchas contaminated biomass and solid city waste, and converting them into asynthesized gas, comprising: a fuel gasification step carried out in aco-current gasogen and in which a fraction of the fuel materialsundergoes combustion with an oxidant and the heat developed in thecombustion is exploited for gasifying the remaining material; and acinders separation, extraction and purification step, wherein cindersare separated and removed from the fuel material after it has underdonethe partial combustion and before it has been gasified; cinders are thenpurified and collected after eliminating from it any remaining fuelmaterial through complete combustion; the fuel material which hasundergone the gasification step without being fay converted to gas (CO)is recirculated by mixing it to fresh material before the latter issubmitted to combustion.
 2. The process for treating solid fuelmaterials according to claim 1, wherein the combustion gas, particularlyCO₂, as developed during cinders purification, is mixed to the oxidantused for the combustion of a fraction of the fuel material.
 3. Theprocess for treating solid fuel materials according to claim 1, whereinthe oxidant is heated to a temperature higher than 400° by means of afraction of the available heat contained in the synthesized gas flowingat a high temperature from the gasogen, before conveying it to supportthe combustion of a fraction of the fuel material.
 4. The process fortreating solid fuel materials according to claim 1, wherein the oxidantincludes a proportion of overheated steam.
 5. The process for treatingsolid fuel materials according to claim 1, wherein the oxidant is fed tothe gasogen under pressure.
 6. The process for treating solid fuelmaterials according to claim 1, wherein plain air is used as an oxidant.7. The process for treating solid fuel materials according to claim 1,wherein air enriched with oxygen is used as an oxidant.
 8. The processfor treating solid fuel materials according to claim 1, wherein pureoxygen is used as an oxidant.
 9. The process for treating solid fuelmaterials according to claim 1, wherein filter dust recovered infiltering the synthesized gas is added to the cinders, after separationand removal and before purification, so that the filter dust undergoesthe same purification process.
 10. An apparatus for carrying out theprocess of claim 1, comprising a vertical, co-current gasogene (1)having an annular combustion area (11) for the combustion of a fractionof the fuel material where the oxidant is fed to both its inner and itsouter sides, and a gasification chamber (12) for gasifying the remainingfuel material, the gasification chamber also being vertical and beinglocated above and downstream of the combustion area (11) in thedirection of fuel material displacement, wherein the floor of thegasification chamber (12) has a device (16, 19, 5, 6) for separating andremoving cinders, comprising a port (19) feeding the cinders and theaccompanying fuel material, through a feeding channel (6), to ascarification chamber (3), where the accompanying fuel material iscompletely burned and transformed into CO₂, while the cinders arecollected, after purification, in a cinder tank a recirculation device(17, 18, 8), located at the top of the gasification chamber (12) forrecirculating the material which has undergone the gasification stepwithout being completely transformed into the synthesized gas (CO),comprises a rotating material distributor in form of shovels (17), therecirculation device conveying the recirculating material to an outletaperture (18) leading into a pipe (8) which feeds the recirculatingmaterial to a duct (7) for the supply of fresh fuel material, where thefresh fuel material is mixed with the recirculating material beforebeing introduced into the gasogen (1) as a fuel mixture.
 11. Theapparatus of claim 10, wherein the vertical co-current gasogen (1)comprises a rotating vertical auger (10) feeding the material upwards inthe annular combustion area (11).
 12. The apparatus of claim 10, whereinthe recirculating device (17, 18, 8) feeds the recirculating fuelmaterial to a feeding duct (7) for the fresh fuel material, which isprovided with a first, substantially horizontal auger, where the freshmaterial is mixed with the recirculating material, and which in turnfeeds the mixture of fresh fuel material and of recirculating material,as fuel, to the vertical auger (10) of the gasogen (1) through a secondsubstantially horizontal auger (9) opening into the vertical shell ofthe vertical auger (10) of the gasogen (1).
 13. The apparatus of claim10, wherein the cinder separation and removal device (16, 19, 5, 6)comprises a distributor unit (16) for distributing, conveying andaerating the material which collects on the floor of the gasificationchamber (12), the distributor unit comprising one or more horizontalshovels (16) which rotate around a vertical gasogen axis, the shovelsbeing oblique to the floor plane, so that they sweep a radial chamberextending for the entire length of tie shovels (16) and having thefunction of smoothly distributing the combustion gas over the entirecross-section of the gasification chamber (12) whilst avoidingpreferential gas flowing channels.
 14. The apparatus of claim 10,wherein the scorification chamber (3) comprises a rotating verticalauger (23) which is supplied with cinders and with accompanying fuelmaterial through a substantially horizontal auger (6) opening in thevertical shell of the auger (23) of the scorification chamber (3) and inthat the purification of the cinders takes place by way of combustion ofthe accompanying fuel material in an annular combustion chamber (24)located in the upper portion of the auger (23) of the scarificationchamber (3), and supplied with oxidant at least at one of the annularperipheries of the combustion chamber.